Impact of Glass Formation on the Thermal Stability of Non-Fullerene Solar Cells
Doctoral thesis, 2023
The world is facing immense challenges such as climate change and the depletion of non-renewable resources, making renewable sources of energy essential for a sustainable future. Organic solar cells are emerging as a promising technology; however, their stability requires significant improvement. The nanostructure of the active layer evolves over time, especially during heating, leading to a degradation in device performance. The focus of this thesis is to improve the thermal stability of the active layer.
Firstly, the thesis studies the impact of mixing on glass formation by introducing the concept of kinetic fragility to organic semiconductors. Model systems of up to eight perylene derivatives are investigated that demonstrate an unprecedented ability to form a stable molecular glass due to aggregate formation. Next, the thesis discusses the impact of isomers on glass formation, which is illustrated with an anthradithiophene-based compound. Binary mixtures of isomers were also found to form aggregates that stabilize the liquid state. In addition, the thesis describes fragility studies of doped systems and establishes that chemical doping can affect the glass formation of a semiconducting polymer. The doped polymer shows a strong tendency for glass formation which is assigned to restricted motion of oxidized polymer chains. Furthermore, the thesis analyzes mixtures of organic photovoltaic acceptors. Binary mixtures of two indacenodithienothiophene-based acceptors are found to co-crystallize, while mixtures of three to five fused-ring non-fullerene acceptors exhibited a reduced tendency to crystallize. Finally, the thesis discusses the use of acceptor mixtures for improving the thermal stability of organic photovoltaic devices. Ternary solar cell devices with two acceptors are discussed that show a stable nanostructure and improved thermal stability compared to binary devices. The thesis also explores hexanary devices that consist of five acceptor molecules, which exhibit excellent thermal stability. Therefore, the use of multicomponent acceptor mixtures is found to be a powerful tool for creating thermally stable organic solar cells.
Firstly, the thesis studies the impact of mixing on glass formation by introducing the concept of kinetic fragility to organic semiconductors. Model systems of up to eight perylene derivatives are investigated that demonstrate an unprecedented ability to form a stable molecular glass due to aggregate formation. Next, the thesis discusses the impact of isomers on glass formation, which is illustrated with an anthradithiophene-based compound. Binary mixtures of isomers were also found to form aggregates that stabilize the liquid state. In addition, the thesis describes fragility studies of doped systems and establishes that chemical doping can affect the glass formation of a semiconducting polymer. The doped polymer shows a strong tendency for glass formation which is assigned to restricted motion of oxidized polymer chains. Furthermore, the thesis analyzes mixtures of organic photovoltaic acceptors. Binary mixtures of two indacenodithienothiophene-based acceptors are found to co-crystallize, while mixtures of three to five fused-ring non-fullerene acceptors exhibited a reduced tendency to crystallize. Finally, the thesis discusses the use of acceptor mixtures for improving the thermal stability of organic photovoltaic devices. Ternary solar cell devices with two acceptors are discussed that show a stable nanostructure and improved thermal stability compared to binary devices. The thesis also explores hexanary devices that consist of five acceptor molecules, which exhibit excellent thermal stability. Therefore, the use of multicomponent acceptor mixtures is found to be a powerful tool for creating thermally stable organic solar cells.
nanostructure.
glass formation
conjugated polymers
kinetic fragility
organic solar cells
Keywords: organic electronics
bulk heterojunction blend
thermal stability
PJ (Physics Origo, Chalmers)
Opponent: Professor Tayebeh Ameri, University of Edinburgh
Author
Sandra Hultmark
Chalmers, Chemistry and Chemical Engineering, Applied Chemistry
Den termiska stabiliteten hos organiska solceller kräver betydande förbättringar för att uppnå längre livslängd och högre hållbarhet. Nanostrukturen hos det ljusupptagande aktiva lagret utvecklas över tid, särskilt vid uppvärmning, vilket leder till en försämring av solcellsprestandan.
Syftet med denna avhandling är att förbättra den termiska stabiliteten i det aktiva lagrets nanostruktur. Blandningar används för att erhålla en hög resistens mot kristallisation och följaktligen bilda stabila molekylära glas. Anmärkningsvärt nog visar solceller bestående av fem olika acceptormolekyler en utmärkt termisk stabilitet. Därför föreslås användningen av acceptorblandningar vara ett effektivt tillvägagångssätt för att utveckla termiskt stabila organiska solceller.
Syftet med denna avhandling är att förbättra den termiska stabiliteten i det aktiva lagrets nanostruktur. Blandningar används för att erhålla en hög resistens mot kristallisation och följaktligen bilda stabila molekylära glas. Anmärkningsvärt nog visar solceller bestående av fem olika acceptormolekyler en utmärkt termisk stabilitet. Därför föreslås användningen av acceptorblandningar vara ett effektivt tillvägagångssätt för att utveckla termiskt stabila organiska solceller.
The thermal stability of organic solar cells requires significant improvement to achieve longer lifetime and higher durability. The nanostructure of the light-harvesting active layer evolves over time, especially during heating, resulting in a degradation in device performance.
The objective of this thesis is to improve the thermal stability of the active layer nanostructure. Mixtures are employed to achieve a high resistance against crystallization and consequently produce stable molecular glasses. Strikingly, solar cells comprised of five different acceptor molecules demonstrate outstanding thermal stability. Hence, the use of multicomponent acceptor mixtures is proposed to be an effective approach for developing thermally stable organic solar cells.
The objective of this thesis is to improve the thermal stability of the active layer nanostructure. Mixtures are employed to achieve a high resistance against crystallization and consequently produce stable molecular glasses. Strikingly, solar cells comprised of five different acceptor molecules demonstrate outstanding thermal stability. Hence, the use of multicomponent acceptor mixtures is proposed to be an effective approach for developing thermally stable organic solar cells.
Subject Categories
Polymer Chemistry
Energy Engineering
Materials Chemistry
Condensed Matter Physics
ISBN
978-91-7905-878-4
Doktorsavhandlingar vid Chalmers tekniska högskola. Ny serie: 5344
Publisher
Chalmers
PJ (Physics Origo, Chalmers)
Opponent: Professor Tayebeh Ameri, University of Edinburgh